FAQ: Can the AD8362 Logarithmic RMS Detector accurately WiMax and LTE?

Document created by enash Employee on Jul 29, 2011Last modified by AndyR on Jan 31, 2012
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Q.

I am looking for an RMS detector which will measure WiMax and LTE signals (OFDM Modulation). Looking at the data sheet of the AD8362, I see no mention of these standards. Can the AD8362 accurately measure the rms power level of such signals?

 

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A.

The short answer is yes. The AD8362 logarithmic detector will have no problem dealing with these signals. When the AD8362 data sheet was written, these wireless standards did not exist. This is why they are not mentioned.

 

Generally speaking, the accuracy of an rms detector will start to degrade as the peak-to-average ratio of the signal increases beyond a certain level. Beyond this level, there will be some internal clipping inside the circuit which will result in small errors. The AD8362 has been extensively tested with signals with peak-to-average ratios as large as 11 and 12 dB (e.g. single and multi-carrier WCDMA and CDMA2000 signals). These peak-to-average ratios are similar to those of WiMax and LTE signals so the AD8362 will not have a problem accurately measuring their signal level.

 

You should think about using a newer device such as AD8363  or ADL5902. These devices have similar rms accuracy to AD8362 but their temperature stability and transfer function ripple are much better.

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